Every once in a while, I accidentally run a red light. A little more often, I’ll speed through a yellow if I’m in a hurry. 99% of my driving, though, is strictly by the rules. It’s not something I have to think about; I just look at the color of the light and do what it tells me.

The traffic light system is easy to follow because it’s relatively simple—there’s little room for interpretation.

If the light is green, you proceed.

If the light is yellow, you slow down and stop.

If the light is red, you stay stopped.

Remember those three rules and you can safely navigate through intersections. Those rules can also make it much easier to eat a healthier diet. That’s according to a new study from The University of Bonn in Germany. Researchers there were able to get people to make vastly healthier eating choices when they replaced traditional food labels with red, yellow, and green stickers.

If you’ve struggled to stick with a diet, there’s a simple, proven system to keep you on track.

Why We Struggle To Eat Healthy

It’s popular to think the problem with eating healthy is education—people don’t know what is or isn’t good for them. But plenty of research suggests the opposite. [1] Most people do have a lot of knowledge about nutrition and can make healthy choices when prompted to do so.

So, if knowledge isn’t the problem, what is?

I think one big factor is that changing your diet is just plain difficult. Once you’ve become accustomed to eating a certain way, it’s really hard to change that habit even if you know you need to. Take smokers, for instance. You’ll be hard pressed to find someone who’s happy with they’re habit. Most people wish they’d quit. Yet, it’s incredibly hard to stop. You can make the argument that cigarettes have powerful and addictive chemicals, but guess what. So does food!

Another factor is that moderation is difficult. It’s been proven over and over that small, gradual change is the best way to create a habit that sticks. But when it comes to food, many of us—myself included—go through the day relatively unaware of what we’ve eaten. You try to cut back on certain foods or drinks but, by the end of the day, you realize you didn’t cut back at all. This can lead to feeling ashamed and giving up (even though it shouldn’t).

These are two big factors working against us, but there’s a psychological tool you can use to overcome them.

Instill Healthy Eating Habits With The Traffic Light Diet

Two health researchers in Germany were curious if the simplicity of a traffic light could be applied to food so that making healthy choices becomes easier—no more trying decipher complex nutrition labels. So, they ran an experiment. They swapped out the labels on 100 different foods, replacing them with simple green, yellow, and red stickers. Green represented healthy foods, yellow was for questionable ones, and red represented foods to be avoided.

They scanned the brains of their subjects as they pondered their shopping choices, and what they learned was pretty surprising. The color coded labels acted as a reinforcement of value—people were willing to spend more money on foods labeled green than on foods labeled red. [2]

Cool! So, the schema of traffic lights can help you make better eating decisions. The only problem? This system doesn’t actually exist. You can’t just go to the store and start making your food choices like this. But you can implement it yourself, and it will help tremendously in making a slow, methodical change to your eating choices that will actually stick.

Here’s how to do it:

Go to an office supply store and buy three sets of sticky notes—one green, one yellow, and one red.

Label everything in your fridge and cupboards with the appropriate note. Green for “I should eat this all the time.” Yellow for, “Okay, but go easy.” Red for “I should eat this very sparingly.”

Each time you eat, take the note off the food and keep it somewhere visible.

Look at your pile of used stickers each time you eat.

This solves the problem of trying to keep track of everything you eat. Rather than writing down each item, you just pull the label off and store it. Keep the extra labels around because you won’t be able to label everything, and sometimes you’ll eat out. For these things, peel the appropriately colored note off the pad and add it to your pile.

Over the course of a day, week, and month, you’ll start to see the proportions of types of food you eat. If you’re feeling hungry, look at your stack for the week. This will remind you if you’ve had too many yellow and red foods, and you can suppress that craving for more and make the healthier choice instead.

This system also works because it doesn’t force you to change your diet overnight. Instead, it makes room for less healthy foods by giving you a system to track them. You can see how much of those unhealthy foods you’re eating over time and start to adjust to less and less.

As you improve your diet, you can start changing some of your yellow foods to red to encourage you to eat even less of them.

The Importance Of Simplicity And Flexibility

When it comes to habit change, two of the most important factors for success are simplicity—you don’t want to burn yourself out with a complex system—and flexibility—you don’t want small mistakes to completely derail good progress.

The traffic light diet works because it excels at both while overcoming some of the big hurdles to eating healthy. It takes little effort to track the foods you eat, and that tracking system lets you make choices about where and how to scale back.

If you’ve thought you should eat healthier, this is one tool that can help you master your psychology and succeed with that change.